Well, I designed it so the schemes apply on a per-site basis. So, if you set a scheme on one network site it won't be set to that on any other network site.
This was kind of a sticking point for me. I wasn't sure if when you activate a scheme if it should be activated just for your account on that site or for your account across the entire network.
I can see how some people would want it to work either way. Like, some people may want to have a different scheme on their account for each site in the network so it's easier for them to remember at a glance which site they're working with.
Even the default scheme and forced scheme options work on a per-site basis. So if, for example, you choose to force a scheme, it will only be forced for everyone on that site of the network; Not every site of the network.
But, would it be useful to allow both ways? I mean, allow people to activate/etc. schemes either on a per-site basis, or on a network-wide basis. If it would be useful, what might be the best way to work that out? How should the plugin determine if the user wants to apply the scheme to their account on just one site or the whole network?
I'm open to adding such functionality. Just not sure what the best way would be to do so.